1. Field of the Invention
The present invention relates to a superconducting device, and more specifically to a superconducting device formed of an oxide superconductor thin film formed on a substrate and having a structure suitable to be assembled in an integrated circuit.
2. Description of Related Art
Typical devices utilizing a superconductor include a so called Josephson device, which comprises a pair of superconductors coupled to each other through a tunnel barrier. The Josephson device can realize a high speed switching. However, the Josephson device is a two-terminal device, and therefore, requires a complicated circuit in order to realize a logic circuit.
On the other hand, typical three-terminal devices utilizing a superconductor include a so called superconducting-base transistor and a so called super-FET (field effect transistor). The superconducting-base transistor includes a tunnel barrier and a base of a superconductor, and can operate at a high speed with a low power consumption, by utilizing high speed electrons passing through the tunnel barrier.
The super-FET is so constructed that a superconducting current flowing through a semiconductor layer portion between a superconductor source electrode and a superconductor drain electrode due to a proximity effect is controlled by an applied gate voltage. This super-FET also operates at a high speed with a low power consumption.
In addition, in the prior art, there has been proposed a three-terminal superconducting device having a channel of a superconductor formed between a source electrode and a drain electrode, so that a current flowing through the superconducting channel is controlled by a voltage applied to a gate formed above the superconducting channel.
However, the above mentioned conventional superconducting devices do not pay attention to integration of superconducting devices. If the above mentioned superconducting devices are applied or used in electronic instruments, it is required to be not only possible to integrate the device or elements but also easy to modify the circuit and to omit a defective element. In addition, in the case that superconducting devices are integrated, it is also required to be capable of realizing a high integration density and of easily planarizing the superconducting devices assembled in the integrated circuit.